First off, has this been done before? If someone knows, reply and it will save some work.

Second off, if this hasn't been done before, what do you think of this spell? I need a spell level for it if it sounds okay. Really, I'm picturing that it could be almost any spell level and it would make sense.

Cackling with vengeful mirth, you point at the victim of your rage as wounds appear on your body. A ray of shadowy energy shoots from your fingertips to strike your target, who sprouts wounds identical to your own.

When you cast this spell, pay any amount of hit points. No effect can reduce or negate the loss of the expended hit points. On a successful ranged touch attack, the target takes an amount of damage equal to the amount of hit points that you spent.

The other correct thing to do would be to put a level-based cap on the damage you can take/deal. So maybe you can only take/deal 2xCL or 4xCL or something. That will stave off some major abuses with instant healing (baring CL shenanigans). Keeps it from doing more damage than other spells--it just can do that damage automatically--for a price.